Chest CT practice and protocols for COVID-19 from radiation dose management perspective

Abstract

The global pandemic of coronavirus disease 2019 (COVID-19) has upended the world with over 6.6 million infections and over 391,000 deaths worldwide. Reverse-transcription polymerase chain reaction (RT-PCR) assay is the preferred method of diagnosis of COVID-19 infection. Yet, chest CT is often used in patients with known or suspected COVID-19 due to regional preferences, lack of availability of PCR assays, and false-negative PCR assays, as well as for monitoring of disease progression, complications, and treatment response. The International Atomic Energy Agency (IAEA) organized a webinar to discuss CT practice and protocol optimization from a radiation protection perspective on April 9, 2020, and surveyed participants from five continents. We review important aspects of CT in COVID-19 infection from the justification of its use to specific scan protocols for optimizing radiation dose and diagnostic information. Key Points • Chest CT provides useful information in patients with moderate to severe COVID-19 pneumonia. • When indicated, chest CT in most patients with COVID-19 pneumonia must be performed with non-contrast, low-dose protocol. • Although chest CT has high sensitivity for diagnosis of COVID-19 pneumonia, CT findings are non-specific and overlap with other viral infections including influenza and H1N1.

Variations in CT Utilization, Protocols, and Radiation Doses in COVID-19 Pneumonia: Results from 28 Countries in the IAEA Study

“…Our study on variations in CT utilization, protocols, and radiation doses demonstrates a lack of There are no specific recommended or target doses in patients with COVID-19 pneumonia, but when evaluation is limited to lung parenchyma, a CTDIvol <3mGy, as recommended for low dose chest CT for lung cancer screening may be sufficient for COVID-19 pneumonia [8]. There are studies on use of high-resolution and ultra-high-resolution chest CT in patients with COVID-19 pneumonia, most studies related to acquisition technique for scanning these patients describe use of non-contrast reduced-dose CT protocol [10,[19][20][21][22].…”

“…But disparities exist in the availability of the preferred diagnostic test, reverse transcription polymerase chain reaction (RT-PCR) for COVID- 19. Also, the high false-negative rate of RT-PCR in early disease and its inability to assess disease severity and progression have led to the growing use of cross-sectional imaging such as CT for diagnosis and assessing disease severity, progression, complications, and treatment response [8]. Although a few single-center studies reported use of chest CT for diagnosis and work-up of patients with COVID-19 pneumonia [9,10], a recent survey suggested that only a very few sites use reduced-dose scan protocols (with lower radiation dose compared to routine or general chest CT protocol) for imaging patients with the suspected or known disease [8].…”

“…Also, the high false-negative rate of RT-PCR in early disease and its inability to assess disease severity and progression have led to the growing use of cross-sectional imaging such as CT for diagnosis and assessing disease severity, progression, complications, and treatment response [8]. Although a few single-center studies reported use of chest CT for diagnosis and work-up of patients with COVID-19 pneumonia [9,10], a recent survey suggested that only a very few sites use reduced-dose scan protocols (with lower radiation dose compared to routine or general chest CT protocol) for imaging patients with the suspected or known disease [8]. Despite reports on chest radiography and non-ionizing radiation-based imaging with ultrasonography [11,12], CT remains the preferred imaging modality in COVID-19 pneumonia.…”

“…Although CT is justified in high disease prevalence sites I n P r e s s with low availability of antigen or antibody assays for the coronavirus, overuse of CT remains an important concern. Although recommendations from the Fleischner Society support use of CT for follow-up and complications in COVID-19 pneumonia, they do not provide guidance on frequency of its use, specific scan protocols and the need to reduce dose for follow-up CT examinations[16].Use of contrast-enhanced chest CT is justified in patients with suspected vascular complications and superimposed necrotizing infection, however, most other pulmonary opacities in COVID-19 pneumonia can be assessed with a single-phase, non-contrast phase chest CT. As opposed to abdomen-pelvis CT, there is little justification for multiphase CT of the chest for most clinical indications in and beyond COVID-19 pneumonia[8,18].…”

Comparison of inspiratory and expiratory lung and lobe volumes among supine, standing, and sitting positions using conventional and upright CT

“…Nonetheless, in a previous study evaluating only inspiratory lung volume in the supine and standing positions (with the subject’s arms down) 6 , the acquired CT data could not provide a prediction of the functional residual capacity or inspiratory capacity because of the lack of expiratory CT data. In this study, to perform both inspiratory and expiratory CT, we used a tube voltage of 100 kVp and automatic exposure control with a noise index of 24 for a slice thickness of 5 mm (relatively low-radiation-dose protocol) because the low-radiation-dose CT with recent scanner technology or reconstruction methods is reported to be sufficient to detect lung cancers 28 , nodules 29 , and pneumonia including COVID-19 pneumonia 30 , 31 and because low radiation dose is reported to be unrelated to the volume or area measurement accuracy 32 , whereas a previous study 6 evaluating only inspiratory CT in the supine and standing positions used a tube voltage of 120 kVp and a noise index of 15.…”